Gas-Insulated Switchgear Assembly Having An Inspection Window For Visually Detecting The Switching Position Of  The Switching Contacts

ABSTRACT

The invention relates to a gas-insulated switchgear, particularly a gas-insulated medium-voltage switchgear, according to claim  1 . In order to satisfy additional safety requirements also with position  2  and  3  disconnectors in gas-insulated switchgears, an inspection glass ( 9 ) is inserted/mounted in the housing ( 10 ) such that the positions of the switching contact elements can be seen directly or indirectly via optical means from outside the housing.

The invention relates to a gas-insulated switchgear assembly, in particular a gas-insulated medium-voltage switchgear assembly, in accordance with the precharacterizing clause of patent claim 1.

In addition to a circuit breaker, which is usually installed in a fixed manner, electrical switchgear assemblies, in particular medium-voltage switchgear assemblies, also contain a disconnector, which is arranged, for example, between the circuit breaker and the busbar current path. This disconnector can assume two or three positions: connected position, disconnected position and possibly grounding position. This disconnector is therefore in the form of a two-position or three-position disconnector.

In the connected position, a connection to the voltage-carrying busbar is produced and, in the grounding position, a connection to ground is produced, for example. In the disconnected position, the movable contact piece of the disconnector is located in a central position between the connected position and the grounding position.

Conventional three-position disconnectors are known as linear-travel switches or knife switches.

In general, disconnectors are used as an independent device in the same gas area as the circuit breaker or in a separate gas area, in particular in the case of double-busbar arrangements. The electrical part of these devices is always part of the gas area and is connected to the drive by means of a gas-tight bushing, which drive is usually located outside the gas area and is generally in the form of a mechanical drive in medium-voltage applications.

In the known double-busbar arrangements, firstly a three-position disconnector and secondly a two-position disconnector (no grounding position) are located in the two separate busbar areas.

Grounding of the outgoing section for the safety of operating personnel, for example during maintenance or installation work, takes place via the grounding position of the three-position disconnector and of the connected circuit breaker. Then, possibly further fitted grounding switches without any switching capacity can be introduced in order to allow for subsequent opening of the circuit breaker. Corresponding electrical and/or mechanical latching devices prevent both the grounding position of the three-position disconnector from being left unintentionally and disconnection of the circuit breaker (if no parallel grounding connection has been connected) and therefore ensure safe grounding of the outgoing section.

The switching positions are transmitted to position displays by means of elements which are mechanically coupled to the drive and are signaled by means of auxiliary switches or proximity sensors. In addition, further positions (such as the grounding position, for example) can be signaled in contactless fashion via reed contacts, which results in redundant position signaling with correspondingly increased reliability.

The visual checking of the switching position prescribed in some application areas by means of direct viewing contact of the switching device in the interior of a gas-insulated switchgear assembly is not possible depending on the construction, position and design, or the positions cannot be clearly identified.

The invention is based on the object of meeting additional safety requirements in two-position and three-position disconnectors in gas-insulated switchgear assemblies, as well.

The object set is achieved in the case of gas-insulated switchgear assemblies of the generic type by the characterizing features of patent claim 1.

Further advantageous refinements are given in the dependent claims.

The essence of the invention is that an inspection window is introduced/fitted in the housing of the switchgear assembly such that the positions of the switching contact elements can be seen from outside the housing directly or indirectly via optical means. Owing to the inspection it is possible to make sure of the switching state achieved or desired. This would be the test, for example, as to whether the disconnector has also actually arrived at the grounded position. The isolated line would thus be demonstrably safe in a working environment.

One further advantageous refinement provides that at least the respective movable switching contact element is provided with a colored or topographical marking, which changes its position with respect to a fixed marking or reference structure depending on the switching position. It is thus easily possible for the presently reached switching position to be tested.

These mentioned advantages only make sense when, owing to a refinement according to the invention, the inspection window is arranged in the housing such that, as a result, the hermetic seal of the housing is maintained. An important factor here is the functional maintenance of the conditions of the gas-insulated switchgear assembly even when an inspection window is introduced. In a corresponding manner, the inspection window can therefore be introduced in a sealed manner into the housing.

In order that the inspection window does not become the bursting element in the event of a pressure overload, in one refinement according to the invention a pressure overload triggering device is arranged within the housing and is triggered markedly before the bursting limit of the inspection window.

In order to permit visual checking of the switching state even when, owing to design reasons, there is no visual access to the switching contact elements of the disconnector, the invention proposes that the optical means comprise at least one mirror, via which the marking or markings can be seen.

One further advantageous refinement provides that, in order to inspect the switching positions in a polyphase arrangement, the position of the inspection window and of the markings is selected in relation to one another in such a way that the latter can be inspected safely.

Furthermore, for a polyphase arrangement one advantageous refinement provides that, in order to inspect the switching positions, one or more inspection windows are provided.

Finally, the design is such that illumination means are provided outside the housing which illuminate the markings for inspection thereof, in order to make it possible to clearly identify the switching state even in poor lighting conditions.

The invention is illustrated in one exemplary embodiment in the drawing and is explained in more detail below.

In the drawing:

FIG. 1 shows switching position assessment in the disconnector ON position, and

FIG. 2 shows switching position assessment in the grounding device ON position.

The visual switching position assessment, see FIG. 1, makes it possible to check the switching state of the switching device located in the interior of a gas-insulated switchgear assembly easily through an inspection window 9 in the encapsulating wall of the housing 10, which is only illustrated partially here. The switching position, i.e. the position of the movable contact 4 in relation to the fixed contacts 1, 2 and 3, is assessed by means of a marking 5 on the, for example, cylindrical contact piece 4. The respective switching position is in this case clearly associated with the position of the marking 5 or other prominent regions of the movable contact in relation to the fixed contacts.

Actuation takes place via the spindle 6, which is connected to the drive 8. The switching position illustrated here is the disconnector ON position.

There are certainly many possibilities for the sensory detection of an end position. In the case of switchgear assemblies which are used in the medium-voltage range, voltages of up to 40 kV are present. Since such switchgear assemblies also serve the purpose, inter alia, of isolating line regions for maintenance and extension work, safe shutdown is without doubt an extremely important requirement for the safety of human life.

In order to be able to determine end positions and disconnection positions, sensors are also used. In this case, however, it is necessary to take into account the fact that even sensors cannot ensure 100% safety. For this reason, the safety systems for clearly evaluating the switching positions should have a redundant design in order to ensure maximum safety provided by the additional visual inspection possibility.

FIG. 2 shows the switching position in the grounding device ON position. This position, as is also the case for any other position, can be inspected in the manner described. In this case, this switching position and the possibility for visually inspecting this position according to the invention is of considerable importance in terms of safety.

The visual switching position assessment is characterized by

-   -   a peripheral or spatially limited marking, which is colored or         identified by machining, on the movable contact of a switching         device, which marking,     -   in a switching position (disconnector ON or grounding device ON)         in a previously determined position in relation to the fixed         contacts or other reference points, which do not change in terms         of their position,     -   can be observed and assessed through an inspection window         directly or indirectly via a mirror or a camera.     -   The marking cannot become detached and is fitted in a fixed         position on the contact such that     -   the reference to the switching position is absolutely clear.     -   The position of the marking ensures that the end position of the         switching position has been reached within the permissible         tolerances.     -   The observation takes place in three-phase systems through a         common inspection window or a plurality of inspection windows         which close the encapsulation in a gas-tight manner.     -   Illumination takes place via separately fitted inspection         windows by means of fixedly fitted luminous means or by means of         movable light sources through the observation window or         additional windows.

These effects mean that there is a possibility for directly inspecting the positions of the switching elements, which is possible despite a switchgear assembly which in most cases is even hermetically enclosed. 

1. A gas-insulated switchgear assembly, in particular a gas-insulated medium-voltage switchgear assembly, having at least one disconnector within the housing of the insulating gas area, characterized in that an inspection window (9) is introduced/fitted in the housing (10) such that the positions of the switching contact elements can be seen from outside the housing directly or indirectly via optical means.
 2. The gas-insulated switchgear assembly as claimed in claim 1, characterized in that at least the respective movable switching contact element is provided with a colored or topographical marking (5), which changes its position with respect to a fixed marking or reference structure depending on the switching position.
 3. The gas-insulated switchgear assembly as claimed in claim 1 or 2, characterized in that the inspection window (9) is arranged in the housing (10) such that, as a result, the hermetic seal of the housing is maintained.
 4. The gas-insulated switchgear assembly as claimed in claim 3, characterized in that a pressure overload triggering device is arranged within the housing (10) and is triggered markedly before the bursting limit of the inspection window (9).
 5. The gas-insulated switchgear assembly as claimed in one of the preceding claims, characterized in that the optical means comprise at least one mirror, via which the marking or markings can be seen.
 6. The gas-insulated switchgear assembly as claimed in one of the preceding claims, characterized in that, in order to inspect the switching positions in a polyphase arrangement, the position of the inspection window and of the markings is selected in relation to one another in such a way that the latter can be inspected safely.
 7. The gas-insulated switchgear assembly as claimed in one of the preceding claims 1 to 5, characterized in that, in order to inspect the switching positions in a polyphase arrangement, one or more inspection windows are provided.
 8. The gas-insulated switchgear assembly as claimed in one of the preceding claims 1 to 7, characterized in that illumination means are provided outside the housing which illuminate the markings for inspection thereof. 